package com.jiazhong.Final.Final03;

import java.util.Scanner;

public class Final03 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        double R=scanner.nextDouble();
        AA aa=new AA();
        System.out.println("圆的面积为"+aa.calArea(R));
    }
}
class AA{
    public final double PI=3.14;

//    public AA() {
//        PI=3.14;
//    }

//    {
//        PI=3.14;
//    }

    public double calArea(double R_R){
        return PI*R_R*R_R;
    }
}
